igii.] 



ATLANTIC AND GULF COASTAL PLAIN. 



311 



Fig. 3. Sketch map showing the relation of land to water in the Middle 

 and Upper Oligocene. Stars indicate fossil plant localities, diagonal lining 

 indicates snhmerged areas. 



of this age are tmknown. This interval comprises the first half of 

 the Miocene age and when renewed stthmergence furnishes ns 

 with a record we find very different conditions from those pre- 

 viously enumerated. Either because of the diversion of the gulf 

 stream to the eastward due to the emergence of peninstilar Florida 

 or as a result of changes in depth off the Hatteras anticline, a cool 

 inshore current seems to have swept southward along the coast and 

 through the Suwannee Strait across northern peninsular Florida, 

 carrying with it a northern marine fauna which replaced the tropical 

 fauna that had previously occupied this region. 



